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PubMed2005

Comparison of three ultrasonic axial transmission methods for bone assessment.

This study compared three approaches to bone assessment using ultrasonic axial transmission. In 41 fresh human radii, velocity of the first arriving signal was measured with a commercial device (Sunlight Omnisense) operating at 1.25 MHz, a prototype based on 1-MHz bidirectional axial transmission and a low-frequency (200 kHz) prototype, also measuring the velocity of a slower wave. Cortical and trabecular bone mineral density, cortical thickness and cross-sectional area were determined by peripheral quantitative computed tomography. Significant but modest correlation between velocities reflects differences in the nature of the propagating waves and methodological differences. Of the higher frequency devices, bidirectional measurements provided stronger correlations with bone properties than did conventional measurements. High-frequency devices were less sensitive to cortical thickness than was the low-frequency device, because higher frequency waves interrogate thinner cortical layers. The results suggest that different axial transmission approaches reflect different bone properties. Therefore, a multifrequency technique might be useful in probing different bone properties.

Aged↗
PubMed2004

Evaluation of the ability of an artificial neural network model to assess the variation of groundwater quality in an area of blackfoot disease in Taiwan.

The back-propagation (BP) artificial neural network (ANN) is applied to forecast the variation of the quality of groundwater in the blackfoot disease area in Taiwan. Three types of BP ANN models were established to evaluate their learning performance. Model A included five concentration parameters as input variables for seawater intrusion and three concentration parameters as input variables for arsenic pollutant, respectively, whereas models B and C used only one concentration parameter for each. Furthermore, model C used seasonal data from two seasons to train the ANN, whereas models A and C used only data from one season. The results indicate that model C outperforms models A and B. Model C can describe complex variation of groundwater quality and be used to perform reliable forecasting. Moreover, the number of hidden nodes does not significantly influence the performance of the ANN model in training or testing.

Arsenic Poisoning↗
PubMed2003

Computer mouse use in two different hand positions: exposure, comfort, exertion and productivity.

The aim of this study was to determine whether there are differences in exposure, comfort, exertion and productivity between a neutral and a pronated hand position when using a computer mouse. Nineteen experienced VDU workers performed a standardised text editing task with each mouse hand position. The wrist positions and movements in the working arm were registered by an electrogoniometer and the muscle activity in the shoulder, two extensors in the forearm and the first dorsal interossei (FDI) was registered by electromyography. The subjects rated perceived exertion and comfort in work with each mouse hand position. Work with the neutral hand position, compared to the pronated, gave a decreased muscle activity in the extensors of the forearm and in the FDI and a trend indicating a decrease in the frequency of deviation movements in the wrist. At the same time, the subjects showed a decreased productivity and they rated less comfort in work with the neutral hand position.

Adult↗
PubMed1997

The impact of keyboard design on comfort and productivity in a text-entry task.

Concerns have arisen that the keyboard is a causal factor in the development of work-related musculoskeletal disorders (WRMDs) among video display terminal (VDT) operators. A number of alternative keyboard designs have been developed with altered geometry in an effort to improve comfort in keyboard operation. However, few data are available to substantiate whether these new keyboard designs are actually effective in reducing discomfort and musculoskeletal problems in users. The purpose of this study was to provide data on the efficacy of certain alternative keyboard design features (e.g. splitting the keyboard in half, and laterally inclining the keyboard halves) in reducing fatigue and musculoskeletal discomfort among keyboard operators. The study also explored the effects of these design features on performance. Fifty subjects performed a text-entry task for one day on a standard keyboard, then were assigned to one of five keyboard conditions for an evaluation period of two days (i.e. 10 subjects/condition). Outcome measures included performance (i.e. keystrokes/h, errors/h) and self-report measures of discomfort and fatigue. The results indicated an initial decline in productivity when subjects began typing on two of the alternative keyboards, but these productivity losses were recovered within the two-day evaluation period. The results also indicated no significant differences between keyboard conditions in discomfort and fatigue. These results suggest a minimal impact of the keyboard design features examined in this study on productivity, comfort and fatigue, at least after two days of exposure.

Adult↗
PubMed1997

Computer mouse operation: is the left-handed user disadvantaged?

A survey of University of Melbourne student-use computers showed that 100% had the mouse installed on the right-hand side. An experiment was performed to determine if the left-handed user was disadvantaged by this arrangement. Times to move the cursor to targets of different sizes and distances showed that left-handed users were not significantly disadvantaged and that, in accord with other tests, they were as good using their non-preferred hand as they were with their preferred hand. As expected, left-handers were superior to right-handed users when using their non-preferred hand.

Analysis of Variance↗
PubMed1998

Influence of mouse position on muscular activity in the neck, shoulder and arm in computer users.

Anecdotal reports of shoulder and arm discomfort related to computer mouse use are common. The aim of this study of ten subjects was to examine the influence of mouse position, relative to the keyboard, on shoulder and arm muscular activity and working posture. Surface electromyography and the Rapid Upper Limb Assessment were used to determine the differences in muscle activity and posture during an editing task in each of three mouse positions. Significantly less anterior (p = 0.01) and middle (p = 0.03) deltoid electromyographic activity was demonstrated when the computer mouse was positioned adjacent to a keyboard without a numeric pad when compared to performance of an identical task with the mouse adjacent to a standard keyboard. Electromyographic activity in trapezius muscle did not differ between mouse positions. Working posture of right handed mouse users is improved by removal of the numeric keypad.

Adult↗
PubMed2002

Real-time transmission of pediatric echocardiograms using a single ISDN line.

We tested the adequacy of a videoconferencing system using a single integrated systems digital network (ISDN) line (128 kilobits per second) for the remote diagnosis of children with suspected congenital heart disease (CHD). Real-time echocardiogram interpretation was compared to subsequent videotape review in 401 studies with concordance in 383 (95.5%) studies. A new diagnosis of CHD was made in 98 studies. Immediate patient transfer was arranged based upon a real-time diagnosis in five studies. In 300 studies, a normal diagnosis obviated further evaluation. A single ISDN line is adequate for transmission of pediatric echocardiograms and it allows for remote management of patients with CHD.

Adolescent↗
PubMed2003

A 2-year prospective study on the effects of depot medroxyprogesterone acetate on bone mass-response to estrogen and calcium therapy in individual users.

The primary aim of this prospective 2-year follow-up study was to investigate the effect of depot medroxyprogesterone acetate (DMPA) on the maintenance of bone mass in women aged 30-45 years. The effects of estrogen or calcium substitution during the second year of follow-up was investigated in seven DMPA users with a high annual bone loss during the first year. The bone mass of 35 users of DMPA and 10 women without hormonal contraception was investigated using peripheral quantitative computed tomography. The baseline cortical and trabecular bone mass (TBM) and the annual change was not different in DMPA users and controls. Over 24 months we measured an increase in TBM of 0.6% and a decrease in cortical bone mass of 0.1% in exposed women. Some but not all of the DMPA users with a bone loss during the first year could be successfully treated with estradiol or calcium. In conclusion, we did not observe an accelerated bone loss in DMPA users aged 30-45 years.

Adult↗
PubMed2002

Comparison of incadronate and alfacalcidol on increased bone turnover caused by ovariectomy in rats.

Mineral density of trabecular bone at the metaphyses of right tibiae was measured by peripheral quantitative computed tomography (pQCT) in ovariectomized rats. Bone mineral density (BMD) decreased dramatically in the 4 weeks following ovariectomy, suggesting that the method is sensitive enough to detect decreased bone mineral density within a short period. Orally administered incadronate dose dependently inhibited the decrease in trabecular bone mineral density induced by ovariectomy, as assessed 4 weeks after surgery. Significant inhibition was observed at doses of more than 0.3 mg/kg/day. Moreover, incadronate at doses of 1 mg/kg or more inhibited the increase in urinary deoxypyridinoline levels induced by ovariectomy, and although slightly increased serum intact parathyroid hormone (PTH) levels were observed, no significant alteration in serum calcium ion levels or urinary calcium excretion occurred. In contrast, while alfacalcidol inhibited the decrease in bone mineral density and the increase in urinary deoxypyridinoline levels at a dose of 300 ng/kg, it significantly lowered serum intact PTH levels and elevated serum free calcium levels as well as urinary calcium excretion. These results suggest that incadronate exerts its pharmacological effect (inhibition of bone resorption and increase in bone mass) by a mechanism different from that of alfacacidol.

Animals↗
PubMed2003

A review of morphology-elasticity relationships in human trabecular bone: theories and experiments.

In the perspective of predicting mechanical from morphological properties of human trabecular bone, the theoretical and experimental relationships between volume fraction, fabric and elastic properties were reviewed.Five data sets of human trabecular bone and two data sets of idealized cells were obtained from various investigators and analyzed statistically with one isotropic and four anisotropic models. For each model, multiple linear regressions were performed to fit the components of both the compliance and the stiffness tensors using volume fraction and in some cases fabric. The adjusted coefficients of determination of the regressions and the average relative errors of the reported versus the predicted tensor norms were calculated. The three anisotropic models that implied a log transformation of the data showed the best results. Excluding the idealized cell data, the adjusted coefficients of determination of these models ranged from 0.80 to 0.95 for the compliance and from 0.80 to 0.94 for the stiffness tensors, while the average relative errors varied between 16% and 55% for the compliance and between 25% and 62% for the stiffness data. The use of volume fraction alone in the isotropic model decreased the adjusted coefficients of determination by 0.03-0.25 and increased the average relative errors by 5-27%. This review confirms the potential of morphology-elasticity relationships for estimation of elastic properties of human trabecular bone using peripheral quantitative computed tomography or magnetic resonance imaging, but emphasizes the need for standardized measurements of mechanical properties at both continuum and tissue level.

Adolescent↗
PubMed1998

Femoral neck strength of mouse in two loading configurations: method evaluation and fracture characteristics.

We evaluated the mechanical strength of murine femoral neck in two loading configurations. The mechanical strength of the left femora of 25 male mice (weight 39 +/- 4 g) were measured in an axial configuration simulating one-legged stance in a human, and the right femora were tested in a configuration simulating a fall to the lateral side, on the trochanter. The reproducibility of the mechanical testing was 1.6% in the axial configuration and 3.7% in the fall configuration. The femoral neck was slightly stronger in the fall configuration. Typically, a load in the fall direction associated with a basicervical fracture, while axial loading resulted in both mid- and basicervical fractures. The linear bivariate correlation coefficient between the mechanical strengths in the two loading configurations was 0.83. Total bone mineral content (BMC), cortical bone mineral content (CtBMC), volumetric cortical bone mineral density (vCtBMD), and cross-sectional cortical area (CSA), measured at the femoral neck by peripheral quantitative computed tomography (pQCT), had a significant relationship with the femoral neck strength in the axial configuration. The coefficient of variation of the pQCT measurements was 9.1, 5.5, 2.3 and 5.5% for BMC, CtBMC, vCtBMD and CSA, respectively. We conclude that the precision of pQCT is moderate in evaluating the femoral neck of the mouse, and vCtBMD is the most reproducible parameter. The mechanical strength of the murine femoral neck can be measured with high precision by the two mechanical testing configurations presented here.

Accidental Falls↗
PubMed2001

Effect of nickel-titanium shape memory metal alloy on bone formation.

The aim of this study was to determine the biocompatibility of NiTi alloy on bone formation in vivo. For this purpose we used ectopic bone formation assay which goes through all the events of bone formation and calcification. Comparisons were made between Nitinol (NiTi), stainless steel (Stst) and titanium-aluminium (6%)-vanadium (4%) alloy (Ti-6Al-4V), which were implanted for 8 weeks under the fascia of the latissimus dorsi muscle in 3-month-old rats. A light-microscopic examination showed no chronic inflammatory or other pathological findings in the induced ossicle or its capsule. New bone replaced part of the decalcified matrix with mineralized new cartilage and bone. The mineral density was measured with peripheral quantitative computed tomography (pQCT). The total bone mineral density (BMD) values were nearly equal between the control and the NiTi samples, the Stst samples and the Ti-6Al-4V samples had lower BMDs. Digital image analysis was used to measure the combined area of new fibrotic tissue and original implanted bone matrix powder around the implants. There were no significant differences between the implanted materials, although Ti-6Al-4V showed the largest matrix powder areas. The same method was used for measurements of proportional cartilage and new bone areas in the ossicles. NiTi showed the largest cartilage area (p < or = 0.05). Between implant groups the new bone area was largest in NiTi. We conclude that NiTi has good biocompatibility, as its effects on ectopic bone formation are similar to those of Stst, and that the ectopic bone formation assay developed here can be used for biocompatibility studies.

Alloys↗
PubMed2002

Effect of load on the early incorporation of impacted morsellized allografts.

Impacted morsellized bone grafts are clinically successful to restore bony defects after failed total hip arthroplasties. The incorporation process seems to be dependent on the location where the reconstruction is performed, which suggests that load could play a role. In this study, we hypothesised that, as in fracture healing, physiological loading has a stimulatory effect on the process of early bone graft incorporation. To test this hypothesis we created a standardised defect in the distal femur of twelve goats. Allograft bone chips were impacted into the defect and a subcutaneous pressure implant was screwed in. With this implant the graft can be loaded under controlled circumstances. Six goats were subjected to a daily loading regime of 3 MPa, the other six were non-loaded. After five weeks the bone mineral density was measured with peripheral quantitative computer tomography. Thereafter, routine histology and histomorphometry were carried out. Bone mineral density was not affected by load. Histology revealed microscopic evidence of bone graft incorporation, which proceeded in a similar way in both loaded and non-loaded specimens. New bone was formed free in the stroma or on graft remnants after osteoclastic resorption of the graft. Only the area of active incorporating bone graft was higher under load. In conclusion, the formation of a new bony structure was not affected by load after five weeks. However, load resulted in a larger area of active graft incorporation at this early stage. Possibly biological and immunological factors govern the early incorporation process independent of the local loading regime.

Animals↗
PubMed1999

An automatic 3D tracking system with a PC and a single TV camera.

We developed a novel system, for tracking a freely moving object (animal) in a limited 3D space, based on a closed loop TV and PC. Instead of using a pair of TV cameras to capture the 3D scene through the pair of its orthogonal projections, the system captures these projections by using a single TV camera. The direct view of the scene (e.g. its ground plan, i.e. projection onto the x-y plane) is captured together with its side projection, (i.e. projection onto the z-x plane) observed in a slanted mirror. The system uses a simple detection algorithm and hardware that were originally developed for 2D tracking of a single, contrast object on a stable and homogeneous background. All three coordinates of the tracked object are evaluated, displayed and stored in real-time, at 25 interlaced frames (samples) per second. The system was implemented on an IBM PC enhanced by an universal I/O board (Kaminsky, Yu, Krekule, I. Universal multifunctional IBM PC I/O board for clinical examinations and experimental research in neuroscience. Physiol Res 1994;43:193-199) and tested by tracking a LED marker, a small living fish in a water tank and a pair of LED markers which were activated one at the time in alternating TV frames thereby demonstrating the ability to simultaneously track two or more objects in 3D.

Animals↗
PubMed2000

An assessment of alternate keyboards using finger motion, wrist motion and tendon travel.

OBJECTIVE: To assess the biomechanical impact of commercially available alternate keyboard designs.DESIGN. A repeated measures study was conducted in a laboratory setting, with planned comparisons of Pitch, Roll and Yaw angles of the keyboards. Ten keyboard conditions were tested. Dependent measures included tendon travel, wrist deviations, and wrist and finger kinematics.BACKGROUND. Various alternate keyboard designs have recently been introduced, which vary Pitch, Roll and Yaw angles, separation distance between keyboard halves, and include other novel features such as cup-shaped depressions for the keys. Yet little objective research has been conducted regarding the biomechanical implications of these various design features. This study attempts to quantify the keyboard designs in terms of several recognized risk factors associated with cumulative trauma disorders that arise with repetitive typing. METHODS: Wrist and finger goniometers were used to measure joint motions during a standardized typing task. 15 experienced typists (8 women, 7 men) served as subjects. Regression equations were used to generate estimates of tendon travel.RESULTS. Tendon travel was affected primarily by Pitch but not Roll or Yaw angles while wrist deviations responded to changes in all three angles. Males had significantly greater amount of tendon travel than female subjects; this difference was only partially accounted for by anthropometry. Differences in joint motion may have a greater impact on the amount of tendon travel.CONCLUSIONS. Alternate keyboard designs can affect tendon travel by as much as 11%. RelevanceAs various alternate keyboard designs are marketed, quantifiable biomechanical data such as that provided by this study, will help to assess their impact on the risk factors for cumulative trauma disorders.

Adult↗
PubMed2000

Shoulder muscle activity in young and older people during a computer mouse task.

OBJECTIVE: Assessment of the age effect in relation to computer work. BACKGROUND: Increasingly, more older people are using computers, while hardware and software are not designed with special consideration of their needs. METHODS: Eight young and nine older females performed different computer mouse tasks. Shoulder muscle activity was recorded from the right deltoid muscle, right and left upper trapezius muscle, and the neck extensor muscles. RESULTS: Mean trapezius muscle activity was significantly higher in the older people (2.8%/3.7% EMG(max) for R/L) compared to the young (1.1%/1.2% EMG(max)). There was a tendency to a higher activity in the older people for the deltoid muscle and the neck extensor muscles. There were small differences in shoulder muscle activation levels between mouse actions, target directions, and between precision demands. CONCLUSIONS: Shoulder muscle activity during computer work is affected by age, but only to a minor extent by the type of computer mouse task. The deltoid and the trapezius muscle activities are low during computer mouse use when there is efficient forearm support by the table. RelevanceAn increasing number of people use computers for hours every day. Intensive use of computers increases the risk of development of work-related musculoskeletal symptoms in the shoulder region.

Adult↗
PubMed2003

Influence of preoperative mechanical bone quality and bone mineral density on aseptic loosening of total hip arthroplasty after seven years.

OBJECTIVE: To test mechanical bone quality and bone mineral density of the femoral head at the day of implantation as indicators for femoral prosthesis loosening. METHODS: Mechanical bone quality of a femoral head slice was assessed by destructive compression testing combined with bone mineral density measurements using peripheral quantitative computed tomography. Fourteen patients with walking pains were attainable for a radiographical follow-up mean 7.1 years after implantation. RESULTS: Radiolucent lines along the stem were evident in 11 of 14 femurs, most of them seen in Gruen zones 7, 6, 1, 3, 14, and showed strong correlations to preoperative bone strength (r=-0.80; P<0.001) and axial stiffness (r=-0.75; P=0.002), yet not to bone mineral density (r=-0.67; P=0.009). Slight varus deviations <3 degrees were noted in six femurs. Preoperative strength was reduced in this femurs to 54% (P=0.006), and stiffness to 61% (P=0.038), while bone mineral density did not differ significantly. CONCLUSIONS: Femoral prosthesis loosening after seven years can be predicted by mechanical bone quality of the femoral head at the time of implantation. Bone mineral density measurements may also indicate future stem loosening but have to interpreted carefully, keeping in mind a poorer predictive value. RELEVANCE: Indications and choice of type of hip arthroplasty should be balanced in osteoporotic bones in particular. While preoperative bone mineral density measurement allows the prediction of mechanical bone quality, its relevance in predicting failure in arthroplasty treatment remains unclear.

Aged↗
PubMed1999

Wrist posture during computer pointing device use.

OBJECTIVE: This research examines individual differences in the wrist postures adopted during the use of two pointing devices (mouse and trackball). DESIGN: A multiple case study of twelve participants was employed. BACKGROUND: The use of pointing devices may lead to musculoskeletal discomfort and injury as a consequence of prolonged exposure to postures involving wrist extension and ulnar deviation. METHODS: Wrist flexion/extension and radial/ulnar deviation was measured while twelve participants completed two standardised tasks involving horizontal and vertical cursor movements respectively. RESULTS: Exposure to extreme ulnar deviation and wrist extension was observed in the use of computer mouse and trackball. The trackball involved decreased ulnar deviation and increased wrist extension, however considerable individual differences were observed. CONCLUSIONS: Some users may be placed at risk of injury by prolonged exposure to the use of such devices, while others may not. A trackball may reduce the exposure to extreme ulnar deviation, but in some cases, a trackball may increase exposure to extreme wrist extension.

Adult↗